Andradite

Formula: Ca3Fe3+2(SiO4)3

Colour: Yellow, greenish yellow to emerald-green, dark green; brown, brownish red, brownish yellow; grayish black, black; may be sectored

Lustre: Adamantine, Resinous, Dull

Hardness: 6½ – 7

Specific Gravity: 3.8 – 3.9

Crystal System: Isometric

Member of: Garnet Group > Garnet Supergroup

Name: Named in 1868 by James Dwight Dana in honor of José Bonifácio de Andrada e Silva, Brazilian mineralogist. d’Andrada had earlier, in 1800, discovered a yellowish-grey mineral from a mine near Drammen, Buskerud, Norway. He described and named this mineral under the name allochroite , from the greek αλλος, another, and χροια, color, due to the change of color of the heated product (with sodium ammonium hydrogen phosphate, reagent in blowpipe analysis) when cooling. Andradite is found in skarns from contact metamorphosed impure limestones or calcic igneous rocks; in chlorite schists and serpentinites; in alkalic igneous rocks, then typically titaniferous.

Type Locality: Drammen, Viken – Norway

Andradite-Grossular Series, Andradite-Schorlomite Series.